How do you enable and configure control state for a control?

To enable and configure control state for a control in ASP.NET Web Forms, you need to perform the following steps:

1. Enable Control State:
   In the control class that you want to enable control state for, follow these steps:
   • Set the 'EnableViewState' property of the control to 'true'. This property enables both view state and control state for the control.
   • Override the 'SaveControlState' and 'LoadControlState' methods of the control class. These methods are responsible for saving and loading the control state.
   Here's an example of enabling control state for a custom control:

   
       using System.Web.UI;
   
       public class MyCustomControl : Control
       {
           private string myControlData;
   
           protected override bool EnableViewState
           {
               get { return true; }
               set { base.EnableViewState = value; }
           }
   
           protected override object SaveControlState()
           {
               // Save the control-specific data
               return myControlData;
           }
   
           protected override void LoadControlState(object savedState)
           {
               // Load the saved control-specific data
               if (savedState != null)
               {
                   myControlData = (string)savedState;
               }
           }
   
           // Other control code and properties...
       }
   

   In this example, the 'EnableViewState' property is overridden to return true, enabling both view state and control state for the control. The 'SaveControlState' and 'LoadControlState' methods are overridden to handle the saving and loading of the control-specific data.
2. Save and Load Control State:
   Within the overridden 'SaveControlState' and 'LoadControlState' methods, you need to save and load the control-specific data using appropriate serialization and deserialization techniques. The saved state can be any serializable object or primitive type.
   • In the 'SaveControlState' method, return the control-specific data that you want to persist as control state. This data will be serialized and stored for later retrieval.
   • In the 'LoadControlState' method, retrieve and assign the saved control-specific data to the appropriate control properties or fields. Perform any necessary deserialization or type casting.
   Note that the control state is automatically persisted and retrieved during the page's life cycle, so you don't need to manually handle the storage or retrieval of control state data.
3. Once you have enabled and configured control state for a control, the control state data will be automatically persisted and available across postbacks. This allows the control to maintain its specific data, even if view state is disabled or if controls are dynamically created or removed.